The growing requirement to reduce noxious gas emissions for transport applications is leading to significant research studies. The development of vehicles that are more efficient in terms of energy consumption forms part of the main objectives. The hybrid drive unit solutions which include an electric motor are witnessing significant development. Hybridization offers the following advantages in particular:                energy recovery during braking. Part of the inertial mechanical power of the vehicle is recovered by the electric motor operating as a generator and stored in the battery;        having an additional degree of freedom in the management of the vehicle's energy consumption. The operating points of the various sources of the vehicle can thus be used with their optimal efficiencies during use.        
In particular, in an electric vehicle with fuel cell (FC) based on hydrogen, hybridization with an electrical energy storage system (ESS) such as an electrochemical accumulator battery, opens the possibility of limiting the dynamics of the fuel cell. The ESS provides the high dynamic power required by the vehicle whereas the FC system can provide the power suited to its own more restricted dynamics (close to the average power of the vehicle). Whereas the electrochemical accumulator battery is a reversible energy conversion system, the FC is a non-reversible energy conversion system.
A control of the distribution of the power provision between the FC and the ESS is necessary in order to optimize the energy consumption. A system for managing the power distribution is generally designated by the term EMS.
An EMS can either implement an off-line optimization (control laws simulated beforehand) or an on-line optimization (adaptation of the control laws to the operating conditions encountered by the vehicle).
The document drafted by M M Vinot, Trigui and Jeanneret and entitled ‘optimal management of electric vehicles with hybrid system’, published within the framework of the IEEE conference ‘Vehicle power and propulsion conference’ held in Lille in June 2010, describes a method of control of the EMS within the framework of a vehicle combining batteries and super-capacitors for the power supply of the electric motor. The procedure proposed in this document makes it possible to minimize the global energy consumption through its optimization computation. However, the minimization of the energy consumption is truly effective only if the running cycle of the vehicle is known a priori. Such a procedure therefore presents a relatively restricted practical benefit in real applications where the running cycle is often not defined in advance.
The document drafted by M M Thritschler, Bacha, Rullière and Husson and entitled ‘Energy management strategies for an embedded fuel cell system on agricultural vehicles’, published within the framework of the 19th ICEM conference held in Rome in June 2010, describes the practical use of the Pontryagin maximum principle adapted for on-line application in a heavy vehicle with fuel cell. This procedure for real-time control of the EMS does not require a priori knowledge of the vehicle driving cycle. The state of charge of the electrical energy storage system is maintained by using the recharging by the FC (conversion of hydrogen). The energy optimization is based on the minimization of the fuel consumption, subject to constraints such as the maintaining of the level of the state of charge in the ESS.
On account of an application to heavy agricultural vehicles in which energy recovery on braking turns out to be almost nonexistent, this procedure does not manage the recuperative braking. Consequently, the efficiency of the system is non-optimal for a conventional automobile application, which alternates frequent cycles of braking and acceleration. Moreover, this procedure is relatively poorly optimized for managing the difference in dynamics of the fuel cell and batteries of accumulators.